Extraction efficiency for

A solute, S, has a Kd between water and chloroform of 5.00. A 50.00-mL sample of a 0.050 M aqueous solution of the solute is extracted with 15.00 mL of chloroform, (a) What is the extraction efficiency for this separation (b) What is the solute s final concentration in each phase (c) What volume of chloroform is needed to extract 99.9% of the solute ... 

For the extraction described in Example 7.14, determine (a) the extraction efficiency for two extractions and for three extractions and (b) the number of extractions required to ensure that 99.9% of the solute is extracted. 

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

Table II. Extraction Efficiencies (%) for Several PAHs using Cyclodextrin-Modified Extraction...

SFE. SFE has been established as the extraction method of choice for solid samples. The usefulness of SFE for soil samples has been demonstrated for carbamate,organophosphorus and organochlorine pesticides. However, SFE is more effective in extracting nonpolar than polar residues. In order to obtain a greater extraction efficiency for the polar residues of imidacloprid, the addition of 20% methanol as modifier is required. Extraction at 276 bar and 80 °C with a solvent consisting of supercritical carbon dioxide modified with methanol (5%) for 40 min gives a recovery of 97% (RSD = 3.6%, n = 10). It is possible to use process-scale SFE to decontaminate pesticide residues from dust waste. ... 

To date most of the work which has been done with supercritical fluid extraction has concentrated on the extraction of analytes from solid matrices or liquids supported on an inert solid carrier matrix. The extraction of aqueous matrices presents particular problems [276-278]. The co-extraction of water causes problems with restrictor plugging, column deterioration, and phase separation if a nonpolar solvent is used for sample collection. Also, carbon dioxide isay have limited extraction efficiency for many water soluble compounds. 

Dimethyl sulfoxide provides a high extraction efficiency for... 

It is the difficult task of the analytical chemist to select the sample preparation technique best-suited for the problem at hand. The more tools there are in the toolkit, the larger the chances of finding a sample preparation technique that offers the desired characteristics. The goal of any extraction technique is to obtain extraction efficiency for the analyte which meets the analytical requirements in the shortest possible time. In some analytical procedures little sample handling is needed [46-49]. 

Figure 3.16 Influence of time on microwave-extraction efficiencies for additives in HDPE. After Jassie et al. [454]. Reprinted with permission from L. Jassie et al., in Microwave-Enhanced Chemistry (H.M. Kingston and S.J. Haswefl, eds), American Chemical Society, Washington, DC (1997), pp. 569-609. Copyright (1997) American Chemical Society...

A study of by Palmer-Toy et al.,12 summarized in Table 19.1, provides further empirical evidence of the utility of techniques coupling heating with efficient protein extraction for the proteomic analysis of FFPE tissue. A specimen from a patient with chronic stenosing external otitis was divided in half and preserved as fresh-frozen tissue or FFPE. Ten micromolar sections of the FFPE tissue were vortexed in heptane to deparaffinize the tissue and were then co-extracted with methanol. The methanol layer was evaporated, and the protein residue was resuspended in 2% SDS/lOOmM ammonium bicarbon-ate/20mM dithiothreitol (DTT), pH 8.5 and heated at 70°C for lh. After tryptic digestion, 123 total confident proteins were identified in the FFPE tissue, compared to 94 proteins identified from the fresh-frozen tissue. Hwang et al. also reported up to a fivefold increase in protein extraction efficiency for samples extracted in a Tris-HCl/2% SDS/1% Triton X-100/1% deoxycholate solution at 94°C for 30 min versus samples extracted in 100 mM ammonium bicarbonate/30% acetonitrile at the same temperature.14... 

Sonication helps improve solid-liquid extractions. Usually a finely ground sample is covered with solvent and placed in an ultrasonic bath. The ultrasonic action facilitates dissolution, and the heating aids the extraction. There are many EPA methods for solids such as soils and sludges that use sonication for extraction. The type of solvent used is determined by the nature of the analytes. This technique is still in widespread use because of its simplicity and good extraction efficiency. For example, in research to determine the amount of pesticide in air after application to rice paddy systems, air samples collected on PUF were extracted by sonication, using acetone as the solvent. The extraction recoveries were between 92% and 103% [21]. 

Water samples were extracted 3 times with 50 ml of petroleum ether and anhydrous Na2S04 was added to the combined 150 ml extract. The extract was evaporated just to dryness and dissolved in benzene for GLC analysis. The extraction efficiency for dieldrin in water was 95%. 

Higher extraction efficiency for the same number of stages, or fewer stages for the same extraction efficiency... 

The flow sheet is similar to the zinc block diagram with two extraction stages, containing three parallel mixers followed by a settler, and two stripping stages with normal mixer-settler arrangement. The pH is monitored and the acidity controlled by the addition of NaOH in the two first mixers. The extraction efficiency for nickel is better than 98%. 

SEE has long been of industrial importance but has only recently been introduced on a laboratory scale. Few applications have been reported for polyphenols but simpler phenolics have been extracted by this method, albeit with addition of methanol to the supercritical fluid. Some potential may be found for online SFE, since very clean extracts (but at low extraction efficiency for phenolic compounds) can be obtained. ... 

Analysis of data from the factorials indicates that pH has a consistently significant effect on compound recoveries. A summary of the effect of pH level on compounds used in the study is given in Table VI. There is also an interaction between pH and primary column sorbent type for some compounds. This interaction suggests that at low sample pH, a C18 column will produce the best extraction efficiencies for phenolic compounds. The effect of adding methanol to the sample before extraction clearly produced odd results when the recovery data from the 24 factorial was analyzed by using half-normal plots. This effect will be studied in future work. Additionally, different elution solvents will be examined as well as new sorbent phases as they become available. 

At an extraction pressure lower than 400 bar the extraction efficiency for camosolic acid is not sufficient. 

Environmental applications of SFE appear to be the most widespread in the literature. A typical example is the comparison of extraction efficiency for 2,3,7,8 -tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) from sediment samples using supercritical fluid extraction and five individual mobile phases with Soxhlet extraction was made (101). The mobile phases, carbon dioxide, nitrous oxide, pure and modified with 2% methanol as well as sulfur hexafluoride were examined. Pure nitrous oxide, modified carbon dioxide and modified nitrous oxide systems gave the recoveries in the acceptable range of 80 to 100%. Carbon dioxide and sulfur hexafluoride showed recoveries of less than 50% under identical conditions. Classical Soxhlet recoveries by comparison illustrated the poorest precision with average extraction efficiencies of less than 65%. Mobile phase choice, still as yet a major question in the science of supercritical fluid extraction, seems to be dependent upon several factors polarity of the solute of interest, stearic interactions, as well as those between the matrix and the mobile phase. Physical parameters of the solute of interest, as suggested by King, must also be considered. Presently, the science behind the extraction of analytes of interest from complex matrices is not completely understood. 

Aqueous samples were extracted for phenol and 4-chlorophenol using pure carbon dioxide in a specially designed phase separator apparatus (111). The extraction efficiency for these phenols was reported to be over 85%, with a RSD of 8% for eight samples. Additional liquid sample extractions have been investigated for the extraction of phenol from a 6M sulfuric acid solution as well as the extraction of the components of commercial soft drinks and orange juice (112-113). In all cases, specifically designed extraction vessels were utilized. 

TABLE II Effect of Modifier Identity on Extraction Efficiencies for Sludge/Fly Ash Using On-Line SFE/GC... 

For the various matrices that were studied, specifically the sludge/fly ash, river sediment and shale rock, certain modifiers were more effective that others in terms of achieving high extraction efficiencies. For the target analytes (PCB s, aromatics, chlorinated aromatics and hydrocarbons) propylene carbonate and benzene achieved the highest extraction efficiencies compared to pure CO2. 

Moreover, under a particular set of conditions, the extraction efficiencies for the SC-C02 system were typically found to be very similar to the corresponding values in dodecane. The strong correlation between the SFE and conventional SX results for the two ions suggests that the solvation behavior of SC-C02 is similar to that of dodecane for the TBP system. Substitution of a stronger Lewis base, such as triph-enyl- (TPPO), tributyl- (TBPO), or trioctylphosphine oxide (TOPO) for TBP, generally yielded higher extraction efficiencies for both uranium and thorium. For both TBPO and TOPO, in fact, extraction was nearly quantitative over the entire range of... 

Feasibility studies have shown that a He-jet activity transport line, with a target chamber placed in the LAMPF main beam line, will provide access to short-lived isotopes of a number of elements that cannot be extracted efficiently for study at any other type of on-line facility. The He-jet technique requires targets thin enough to allow a large fraction of the reaction products to recoil out of the target foils hence, a very intense incident beam current, such as that uniquely available at LAMPF, is needed to produce yields of individual radioisotopes sufficient for detailed nuclear studies. We present the results of feasibility experiments on He-jet transport efficiency and timing. We also present estimates on availability of nuclei far from stability from both fission and spallation processes. Areas of interest for study of nuclear properties far from stability will be outlined. 

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